Generally speaking, there are three modes for information transmission in an Ethernet including unicast, broadcast and multicast. The unicast mode is mainly used for the information transmission between two devices of a network, and the data encapsulation of the unicast mode is performed using IP address in any one of class A, B and C. The broadcast mode is used for the information transmission from one device to all the other devices in a network. During a broadcast, all digits in the part of host address in the destination IP address carried in the data packet are set as 1. The multicast mode is used for the information transmission from one device to multiple designated devices in a network, and the multicast data packet is encapsulated using IP address in class D.
The multicast technology has achieved a high effective point-to-multipoint data transmission in a network, which can effectively save network bandwidth and reduce network load, and thus the multicast technology is the optimum multipoint communication technology. The multicast technology has been widely used in multipoint communication service fields such as Web Television (TV), tele-education, real-time transmission of finance information, multimedia conference, game and emulation. A controllable multicast requires an access device to be served as a multicast service control point which is able to achieve a controllable access of video program, and may configure multicast right of each user, e.g., whether a user is allowed to receive a multicast program, which program a user is allowed to receive, program number that a user is allowed to receive simultaneously. The multicast right must be configured in a real time manner through a command line or a network management interface. FIG. 1 is a principle block diagram for performing controllable multicast video services in an IP Metropolitan Area Network (MAN). As shown in FIG. 1, after a user demands a video service, his right information will be generated by a video service support system/user management system and delivered to an access device. The access device guarantees that the configuration is instantly effective. The video service support system in FIG. 1 includes a head-end system, a user management, a program management, a right management, a playbill management and a charging management.
In the multicast technology, how to charge each user is a problem necessarily to be solved. There are two solutions for the problem in the prior art.
1. A first solution is a monthly fee mode.
In this solution, a terminal device of IP multicast such as a Set Top Box (STB) or a computer may join or quit a multicast group at any place in any time. The multicast router or multicast Layer 3 switch only needs to learn whether there is a terminal device of a physical sub-network belonging to a multicast group instead of saving the member relationship between terminal devices.
FIG. 2 is a principle diagram illustrating a system adopting monthly fee mode in the prior art. As shown in FIG. 2, when a user demands a program, an STB or a computer delivers a packet for joining a multicast group, and then an access device sends a request for joining the multicast group to an upper layer router or a program source of the Asynchronous Transfer Mode (ATM)/IP network. After joining the multicast group, the program source issues a video stream to the access device, and then the STB or computer will receive the video stream issued by the access device.
Since the access device is only able to learn whether a user is existed in a port, the access device is unable to learn how many users are existed in a port, not to mention to learn which user is online. It is impossible for the access device to learn when a specific user begins on line, when the user becomes off line, and which program the user has demanded. Moreover, it is impossible for the access device to generate an on-demand bill for a specific user. That is to say, in such a case, there is no record for a user demanding a program, and the charging of the access device may only use the monthly fee mode. The drawbacks of this solution are as follows.
(1) Lacking a valid user management mechanism: a user may join a multicast group and leave the group randomly. The multicast source is unable to learn when the user joins and quits. And there is a lack of a valid measure to control the transmission direction and range of the multicast information in the network.
(2) Lacking a valid charging measure: since the multicast protocol has no relationship with the charging, the multicast source is unable to learn when a user joins or quits and cannot calculate how many users are watching a multicast program within a time period, it is impossible to perform an exact charging.
(3) In the monthly fee mode, a user is able to demand programs randomly as long as he has paid the monthly fee, which seems to be very economical. In fact, only the users who are often on-line feel it is really economical. For the users who are seldom on-line, the monthly fee mode is uneconomical. Since a common user occupies little network resources in the aspect of network traffic and occupying time and is charged with no difference. The passion of such a common user will be affected, so that some potential users will flinch.
(4) The monthly fee mode may also lead to another psychology, i.e. some users consider “nonuse is uneconomical” because the monthly fee has been paid, so that they may watch many programs, even some programs they don't like, which leads to the waste of network resources and the network congestion, the impact the monthly fee mode is severer especially in the on-line rush hour phase, thereby restricting the profit and scale development of merchant finally.
(5) The simple monthly fee mode is a very non-flexible charging mechanism, which will lose many users. With the simple charging mechanism, the profits achieved by the network operator are very small while more resources and profits are lost.
2. A second solution is charging based on demanding times.
In this solution, the STB/computer performs interaction with a video server (video source) through a web page. The video server issues an Electronic Program Guide (EPG) to the STB/computer, a user selects the program he wants to watch using a remote control. The charging system performs the charging based on the time the user demands a program.
In this solution, the charging is performed based on times for clicking a program. It is impossible to learn the on-demand duration. Since it is impossible to perform the charging based on the on-demand duration, the charging thereof is very unreasonable. Moreover, under the circumstances that network resources are very scarce, if a user is frequently off line, it is necessary for the user to click multiple times to watch one program, thus it is unreasonable to perform the charging based on the demanding times. The single and non-flexible charging mode leads to negative influence for the development of service.
As can be seen from the existing solutions, the existing monthly fee mode and the demanding times based charging mode lead to negative influence for the development of service, because there are a lack of a valid user management mechanism and charging modes of the monthly fee mode and the demanding times based charging mode are single.